Hi Jimbob T,
The alternative is Videomerge.
Please refer to the below link
ChromaKey, GreenScreen Key, and BlueScreen Key are not included in Premiere Elements Mac.
Some suggest Videomerge as the alternative. I do not. But Videomerge is not THE alternative.
Instead, I prefer the Difference Matte as a substitute for the 3 absent keying effects. Please check out my blog post on that which includes
the how to.
The suggestion has met with good results according to the feedback that I have gotten to this.
I am strictly a Premiere Elements Windows user who does not prefer Videomerge even in Windows.
Please review, consider, and let us know the outcome.